Multielement helix antenna



Oct; 28, 1952 A. E. MARSTON ETAL MULTIELEMENT HELIX ANTENNA Filed Dec. 1, 1949 awe/WW ARTHUR E. MARSTON M. DONALD ADCOCK ATTORN EY Patented Oct. 28, 1952 UNITED STATES PATENT OFFICE MULTIELEMENT HELIX ANTENNA Arthur E. Marston and Mack Donald Adcock,

Washington, D. 0.

Application December 1, 1949, Serial No. 130,575

4 Claims. (01. 250-3351) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) 2 invention will become apparent upon a careful consideration of the following detailed description when taken in conjunction with the drawings in which:

Fig. 1 is a typical illustration of the preferred embodiment showing a pair of substantially identical helical elements disposed about a common axis in accordance with the present invention and Fig. 2 is illustrative of the field radiation patterns obtainable from a conventional single helical antenna and the multi-element helical antenna shown in Fig. 1.

Referring in particular to .Figure 1 there is Ventional helical antenna PeFating as i t illustrated a pair of helical antenna elements fire antenna i i i 15 arranged in accordance with the teachings of along the lqngltudmal Is that the Ion the present invention. Helices I3 and I4 are of paitt.ern denved h f for purpos.es 0 the end-fire type, wherein the maximum radiacelvmg or transmitting electromagnetic energy, is not symmetrical This is of course a serious {Bach hghx 1S m the dn'efctlqn along Its disadvantage for most any type of antenna use longltpdmal i and t polanzatlon each when it is desired that the pattern therefrom hehx 1S ramming}, (flrcular' The.hehca1 anadequately cover a certain field. tennas illustrated m Fig. 1 are hereinafter de- The present invention provides a combination scnbed the purposes of transltnsimn of elec of circularly polarized helical elements arranged 5 tromagmitlc etlergy but h Prmclple of the and disposed in a unique manner as fuuyde present invention, as applied in the preferred scribed hereinafter, about a common axis, and emPodlment 1S equally as applicable in an operable as a single end fire antenna The helical antenna operative for the reception of ferred embodiment of the present invention electromagnetlcenergy. Helical elements I3 and vides many advantages over that of a Single I 4 are substantially identical, both resonant at helical antenna element; the most prominent the same frequency or band of frequencies at advantages are with respect to improvements in which they and both disposed on the symmetry of the field radiation pattern a common longitudinal axis indicated by dotted tainable from a ingle helix and to improve line '5. The antennas are centrally positioned ments in the circularity of polarization. on a ground Plane and are energized, by a t i accordingly an bject of th present, two wire transmission line 20. Inner conductor ti t provide a new and improved helical 22 of transmission line 20 is connected to the t first turn I8 of helix I3 and outer conductor 23 It i a, f rther object f th present invention is connected to the first turn I1 of helix I4. The to provide a new and improved multpelement 4o outer conductor 23 being the shield of transmishelical antenna offering an improvement in the sion line 20 and which is also terminated in the symmetry of the field radiation pattern over that ground p ane l2. of a single helical antenna. We have discovered a property of the helical Another object of the present invention is to antenna With respect to the phasing thereof that provide a new and improved multi-element helbears a direct relationship to the angular orienical antenna ofiering improved circularity of tation of the helices about their longitudinal axis. polarization for either transmission or reception More particularly it has been proven, as an exover that generally offered by a single helical ample, that with two helices energized in ph t and with the two helices oriented so that their Still another object of the present invention first turns point in the Same direction, he e is is to provide a new and improved multi-element helical antenna wherein the elements are disposed about a common axis to eliminate an array ac r- Ffurther objects and attainments of the present a zero phase difierence therebetween. However it was further shown that, if one of the helices is rotated about its longitudinal axis, say as per example again, by there results a 90 phase difference between the two helices. This phasing principle is true for any angular orientation distinction between any number of helices.

The converse of this phasing principle with respect to their angular orientation, and which is more directly applicable to the present invention, is equally true. That is if, for instance, two helical antennas are energized with an 180 phase distinction, then rotating one of the helices by 180 will restore the in phase radiation condition.

With a single helical antenna as a simulated single wire antenna, the field pattern obtainable therefrom is found to be asymmetrical about its longitudinal axis. This asymmetry is primarily caused by the asymmetry of the radiation pattern of a single turn of the individual helices. We have found, however, that this asymmetry can be corrected by interwinding a second helix with an axis common to the first helix. The second helix is identical with the first helix, that is having the same physical dimensions and accordinglythe same resonant frequency. To permit interwinding of the two helices, to be operable as a double wire antenna in accordance with the principles of the present invention, the two helices must necessarily, therefore, be oppositely oriented.

Interwinding the helical elements about a common axis has shown to be more advantageous then if they were placed side by side as in any array. The most prominent advantage of coaxially interwinding the helices is eliminating the array factor, that is the phasing of the elements, as described herein, may be more readily carried forth by eliminating any phase distinction due to the spacing of the elements.

It is known in the art that when two antennas are energized in phase, the fields therefrom will add, and it is also known that when they are energized 180 apart the patterns from each antenna will be distinct with a null ,therebetween. Toovercome the phase distinction between helices due to the necessary opposite angular'orientation of the helices, as hereinbefore described, andto obtain a zero phase distinction between helices sov that the fields therefrom add, the helices are energized 180 apart by the line 22). Any means known to the art, however, may be employed rather than the means shown. to energize the helices in phase opposition.

The. present invention is, of course, not to be limited to the number of helices shown in Fig. 1', moreover, the more helices employed (to a practical limit), the more symmetrical the pattern therefrom; will. be. ploying two or more helices being that they must be energized with a phase distinction corresponding to the. orientation distinction between helices. results are obtained when the helices are pro gres'sively oriented, that is, if four helices were employed they would be oriented, with respect to their common longitudinal axis,- at 90, 18.0 and. 270?.

With reference to.-Fig. 2, there is showna typical pair of antenna patterns A and B, pat:- tern Av being illustrative of a non-symmetrical radiation, pattern substantially as that derived. fmma single. helix antenna and pattern B being illustrative of the-unmoved symmetrical pattern.

produced by the'multi-element helical antenna of the present invention... The pattern A contains an accentuated. minor. lobe on; one side of its. axis and as hereshowmthis lobe i-sto.= the: left of the axis. By employing twohelical antennas The only requirement in em- It was found, generally, that the best 4 as described above, a symmetrical pattern as that shown in B is obtained.

Directly in accordance With the above outlined principle relating to improvements in the symmetry of the field radiation pattern, is the circularity of polarization. Improvement in circularity of polarizationhas been found to follow in the same manner, with respect to the helices, as the improvements in the symmetry of the field pattern.

A helical antenna constructed in accordance with Fig. 1 has a spacing between turns of .24 of the operating wavelength, at which they are end-fire, and the diameter of the turns is .31 of the operating wavelength. The number of turns was decided upon in accordance with the beam width desired and is not factor in determining the resonant frequency.

Although a certain specific embodiment of this invention has been herein disclosed and described, it is to be understood that it is merely illustrativeof this invention and modifications may, of course, be made without departing'from the spirit and scope of the invention as defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An end-fire helical beam antenna system comprising a plurality of similar, resonantheli cal filament antennas interwound in the same direction about a common axis, each filament having a turn diameter greater than the turn pitch and being such that one turnlength thereof substantially equals one wavelength at the operating frequency, one end of said filaments bein open to cause said antenna toresonate at said operating frequency and the other end of said filaments being terminated in a feed system to produce a symmetrical single-lobe pattern of circularly polarizedradiation.

2. An end-fire helical beam antenna system comprising a plurality of similar, resonant hellcal filament antennas interwound in the same" direction about a common axis,- each filament havinga turndiameter greater than the turn pitch and being such that one turn length thereof substantially equals one wavelength at the op era-ting frequency, one endof said filaments be ing open to cause said antenna to be resonant at said; operating frequency, the first turn of each of said filaments having a distinct angular orienrection about a. common axis, each filament" hav ing, a turn diameter greater* the pitch and being such that one turn length thereof substantially equals one wavelength: at the operating frequency, the turns of one of said helical" fila merits being: arranged; in; spatial opposition with respect to the angular orientation of the other of" said' filaments about. said axis, one end of said" filaments being open to" cause. said antenna-to be resonant at said operatin frequency, and meaneconnecting. the other end. of; said; filaments-in electrical phase opposition to produce a symmetrical single-lobe response pattern to circularly polarized Waves.

4. An end-fire helical beam antenna system comprising a pair of similar, resonant helical filament antennas interwound in the same direction about a common axis, each filament having a turn diameter greater than the turn pitch and being such that one turn length thereof substantially equals one wavelength at the operating frequency, one end of each of said filaments being open, the first turn of each of said filaments having a distinct angular orientation relative to said axis, a ground plane for said pair of helices, coaxial transmission line means including an inner conductor connected to one of said pair of filaments and an outer conductor connected to the other of said filaments and said ground plane for energizing said pair of filaments with an electrical phase distinction in accordance with said orientation distinction to produce a symmetrical single-lobe response pattern to circularly polarized waves.

ARTHUR E. MARSTON. M. DONALD ADCOCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Electronics, pages 109 to 111, April 1947. 

